Presently, as a next-generation communication standard of LTE (Long Term Evolution) systems, sophistication of LTE-Advanced is being developed. In LTE-Advanced systems, carrier aggregation (CA) technique is introduced to achieve a higher throughput than that of the LTE systems while ensuring backward compatibility with the LTE systems. In the carrier aggregation, a component carrier (CC) having the maximum bandwidth of 20 MHz supported by the LTE systems is used as a basic component, and it is designed to achieve broader band communication by using these multiple component carriers simultaneously.
In the carrier aggregation, user equipment (UE) can use multiple component carriers simultaneously to communicate with a base station (evolved NodeB: eNB). In the carrier aggregation, a highly reliable primary cell (PCell) to ensure connectivity to the user equipment and a secondary cell (SCell) additionally configured for the user equipment during connection to the primary cell are configured. The primary cell is a cell similar to a serving cell in the LTE systems and serves as a cell to ensure connectivity between the user equipment and a network. On the other hand, the secondary cell is a cell configured for the user equipment in additional to the primary cell.
In the LTE standard, as illustrated in FIG. 1, Intra-band Non-contiguous CA, where multiple discontinuous carriers are bounded in the same frequency band, can be applied. In the Intra-band Non-contiguous CA, as illustrated, the carrier aggregation is performed with the multiple separated carriers in frequency band “BandX”. In 3GPP TS 36.101, combinations of Intra-band Non-contiguous CA capable carriers as illustrated in FIG. 2 are defined. Here, “CA_41A-41C” indicates that carrier 41A of a bandwidth (BW) class A (for example, 20 MHz) and carrier 41C of a BW class C (for example, 40 MHz) having a frequency higher than that of the carrier 41A in band 41 are a CA capable combination. Also, “CA_41C-41A” indicates that carrier 41C and carrier 41A having a frequency higher than that of the carrier 41C are a CA capable combination.